Fabry-Perot Modulators as Wavelength Sensitive, Switchblade Detector Arrays and Their Integration into Smart Pixels.

The work of the past three years has focused on VCSSEL-based free-space interconnects which appear to offer significant advantages for smart pixel applications. Todays vertical cavity lasers VCLs are the choice for short distance optical links, computer interconnects, and smart pixels. Their low threshold currents, relatively low power consumption, and low operating voltage, make them compatible with simple drive circuits. High modulation bandwidth can be achieved without additional pre-bias circuitry. VCLs with a record 3 dB bandwidth of 15.3 GHz at only 2.1 mA of bias current have been reported from UCSB. The small diameter devices have peak output powers suitable for optical interconnect applications. Much of the recent improvement can be attributed to the introduction of a thin dielectric aperture, formed by lateral wet oxidation of high Al content AlGaAs compounds, in the laser cavity. The aperture provides good lateral current confinement and reduced optical losses, resulting in more efficient, smaller size devices with very low threshold currents. Another advantage of small diameter VCLs are their highly divergent beams. The beams reaching the back side of the substrate fill integrated microlens enabling high numerical aperture focusing or collimation into low diffraction beams. With these integrated components, coupling into fibers and collimation for free-space systems can be realized with no external optics. We have developed a technology for fabrication of refractive microlens in GaAs and in InP for integration with VCLs and with detectors, respectively. We considered the application of VCLs in a free-space optical system to board-to-board interconnects that would, provide a high speed, low power option to back plane data buses.